The present invention relates generally to a torque limiting handwheel for preventing manual valves from being damaged because of the excessive application of torque during the opening and closing operation of the valves.
Because of the variety (manufacturer and size) of valves, it is difficult for operators to keep up with the torque limits of each particular valve. The application of excessive torque has been the cause of many valve failures. Operator judgment becomes a frequent substitute for a torque wrench. When excessive valve seat leakage occurs, it is a natural tendency to apply excessive torque to the valve to correct the valve seat leakage. It is costly and time consuming to replace the damaged valve seats due to excessive torquing by the operators.
It is, accordingly, a general object of this invention to develop a torque-limiting handwheel which when installed on a valve, prevents the valve from being damaged through the application of excessive torque during operation of the valve.
Another more particular object of the invention is to provide a torque-limiting handwheel wherein an almost infinite range of maximum torque levels may be achieved.
Yet another object of the invention is to provide a torque-limiting device for manual valves wherein a common set of hardware can accommodate a wide range of valves having different allowable operating torques.
Another object of the invention was to devise a torque limiting feature for manual valves which can be applied as an integral part of a valve handwheel, the valve lazy rod, separate from the valve or be incorporated into a valve wrench.